Ultra-processed food vs whole food: which has more of an impact on weight?
As our lives become more and more time constrained, the food industry has stepped in to make it more convenient and faster to eat. Unfortunately, this has led to intake of ultra-processed food being the mainstay of our intake, which has led to a rise in obesity and many health conditions.
Typically these foods come from cheap ingredients that can be put together easily by machines, and they deliver a taste appeal that has people coming back for more and more. Most of this taste is due to the chemical combination of sugar, fat and salt. (For a good in depth analysis read Mindless Eating by Brain Wansink or Fast Food Nation by Eric Schlosser).
Interestingly, the National Institute of Health conducted a study to evaluate if it is truly the processed nature of the food eaten that drives people to eat more than needed and thus gain weight.
The study compared an ultra-processed food diet to a diet of whole food or minimally processed food.
20 healthy and stable weight adults – both men and women were recruited to participate. They lived for 4 weeks in a National Institute of Health facility in which meals were all prepped for them. Each person was assigned randomly to either an unprocessed whole food plan (whole veggies cooked, steamed rice, real fruit and animal based protein like chicken breast) OR an ultra-processed plan (things like white bread, breakfast cereals, canned fruit, pre-packaged processed meats, etc). After 2 weeks the participants switched to the other diet plan.
The meals were all matched for content of calories, but the ultra-processed plan provided more calorie dense foods per bite due to lack of fiber compared to the unprocessed plan. People on the processed diet also seemed to eat faster, potentially due to the ease of chewing food that doesn’t contain a lot of fiber. Eating faster is known to delay the signal to the brain indicating that you are full, thus the tendency to eat more than needed.
With the study being highly controlled with factors evaluated in participants including intake of all calories, as well as metabolic parameters it makes the findings even more interesting. Health markers such as hormone levels and blood sugar levels were tracked to allow for evaluation of what was happening in the body based on the diet being consumed. Many other studies have found correlation between processed food and weight gain, but none were controlled the same way this study was to show truly that the ultra-processed food intake changes how the body reacts to nutrients and what it does with them that is so detrimental.
What did they find?
Looking at some of the hormone levels evaluated shows that those eating unprocessed diet had a higher level of a hormone that suppresses appetite (a hormone called PYY) and lower levels of a hormone that signals hunger – ghrelin. The same hormones were evaluated in those on the ultra-processed plan and the hormone levels were exactly opposite – they had more of those that increased hunger and less of those that suppressed appetite.
Considering this for a take home message for people with diabetes, I can’t help but quote a favorite author of mine – Michael Pollan. He says “Eat Food, Not too much, mostly plants”. How does this meet the need for those living with diabetes? When we work so hard to count carbs, take insulin to match our food intake, control our weight and workout to contain our glucose levels, a study like this brings to light the fact that what we eat plays a big role in how our diabetes and long term health are managed. Having problems with the typical burrito with processed flour wrap, enchilada sauce and refried beans? Perhaps it isn’t the wrong amount of insulin or a wrong carb count or even the bolus timing. It may in fact be the content of the meal that needs evaluation and adjustment. Eating clean, real food that doesn’t have a laundry list of ingredients is a good place to start with trying to reign in glucose control and maintain overall health for the long haul!
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